1. Field of the Invention
The present invention relates to combustion, and more particularly to ignition systems such as in gas turbine engines.
2. Description of Related Art
A variety of devices are known for initiating combustion, for example in a gas turbine engine. Many gas turbine engines use spark igniters for ignition. One or more spark igniters are positioned to ignite a fuel and air mixture to initiate the flame in the combustor. These typical igniters provide ignition energy intermittently, and the spark event must coincide with a flammable mixture local to the igniter in order for engine ignition to occur. Often this means fuel will be sprayed toward the combustor wall near the igniter to improve the chances of ignition. This increased concentration of fuel can wet the igniter, making it more difficult to light and can lead to carbon formations which will also make ignition more difficult.
Although the igniter is used for a very minute portion of the life of the engine, a great deal of care must be devoted to it such that it does not oxidize or melt in the course of the mission when it is not functioning. Typical igniters can fail instantaneously and without warning, which also requires special design considerations in anticipation of failure. The high voltages that are used to generate the spark can often find alternate paths in the circuit leading to the spark surface across which they can discharge and in such cases, the igniters can fail to provide an adequate spark for engine ignition. The high voltage transformers required to generate the arc are heavy and require heavy electrical cables and connectors. The sparks have trouble generating enough heat to vaporize cold fuel in cold conditions. Fuel must be in vapor form before it will ignite and burn. High velocity air, as may occur in altitude flameout situations can quench the spark out before it ignites significant fuel. The ignition process can interfere with electronic device functions through stray electromagnetic interference (EMI). Sparking systems have difficulty in maintaining a lit combustor under very low power or other unstable or transient mode of operation. Often, pilots might choose to leave the igniters on for an extended period of the mission to prevent flameout, such as during bad weather. Leaving the spark plugs on for the entire mission can lead to early igniter deterioration and failure.
Such conventional methods and systems have generally been considered satisfactory for their intended purpose. However, there is still a need in the art for systems and methods that allow for improved ignition. There also remains a need in the art for such systems and methods that are easy to make and use. This disclosure provides a solution for these needs.